As hardware for reproducing and storing high resolution or high quality video content is being developed and supplied, a need for a video codec for effectively encoding or decoding the high resolution or high quality video content is increasing. According to a conventional video codec, a video is encoded according to a limited encoding method based on a coding unit having a predetermined size.
Image data of a spatial domain is transformed into coefficients of a frequency domain via frequency transformation. According to a video codec, an image is split into blocks having a predetermined size, discrete cosine transformation (DCT) is performed on each block, and frequency coefficients are encoded in block units, for rapid calculation of frequency transformation. Compared to image data of the spatial domain, coefficients of the frequency domain are easily compressed. In particular, since an image pixel value of the spatial domain is expressed according to a prediction error via inter prediction or intra prediction of the video codec, when frequency transformation is performed on the prediction error, a large amount of data may be transformed to 0. According to the video codec, an amount of data may be reduced by replacing data that is consecutively and repeatedly generated with small-sized data.
In particular, a method of adjusting a value of a reconstructed pixel as much as a sample adaptive offset (SAO) may be employed during an operation of encoding and decoding video so as to minimize an error between an original image and a reconstructed image.